Various synthetic polymers are typically produced from petrochemical sources via well-known chemical processes. In recent years, the industry has renewed its focus on biopolymers from environmentally friendly, renewable sources of plants, animals and other living organisms. Extracting the biopolymers from their natural sources often employs large quantities of volatile organic solvents or other undesirable chemical solvents. It is a desirable next step to employ a “green solvent” to extract and process biopolymers.
In recent years, ionic liquids have been extensively evaluated as environmental-friendly or “green” alternatives to conventional organic solvents. Ionic liquids have been used to dissolve or treat cellulosic materials and starch. Such applications are described in U.S. Pat. Nos. 1,943,176; 6,824,599; WO 05/17001; WO 05/17252; and WO 05/23873.
Generally speaking, ionic liquids refer to a specific class of salts which are liquids at temperatures of 100° C. or below. Ionic liquids have very low vapor pressure and generate virtually no hazardous vapors. Moreover, ionic liquids are composed of charged species that provide a highly polar medium useful in various applications, such as extraction, separation, catalysis and as chemical synthesis media.
Additionally, ionic liquids have been shown to be effective in applications where water-based chemistry can be problematic (for example, applications involving proton transfer or nucleophilicity), or in applications where certain coordination chemistry could have a damaging effect on the substrates involved.
Therefore, it is desirable to take advantage of the highly polar and environmentally friendly nature of the ionic liquids in modifying and/or derivatizing biopolymers to provide modified biopolymers.
It is also desirable to provide modified biopolymers useful in various applications via green chemistry employing environmentally friendly starting materials and processes.